Using Outlook 2003 Exchange Recovery Mode with a Dial Tone Database


The new Outlook 2003 feature known as Cached Exchange Mode replaces the Offline Folders mode of previous versions of Outlook. In Outlook 2003, the local cache of mailbox data still resides in an encrypted .pst file (with the file extension .ost), but Cached Exchange Mode adds significant capabilities to the previous offline mode. For example, Cached Exchange Mode provides a function called Exchange Recovery Mode. (For users with versions of Outlook prior to Outlook 2003 with Exchange 2003, Exchange Recovery Mode is not available.)

After an Exchange database has been reset, users running Outlook 2003 in Cached Exchange Mode see this dialog box:

Exchange is currently in recovery mode. You can either connect to your Exchange server using the network, work offline, or cancel this logon.

With previous versions of Outlook, this message does not appear. Instead, if a user chooses to work online, the previous .ost file becomes unreadable because a new key from the new mailbox overwrites the encryption data associated with the previous mailbox. The .ost file is tightly linked to a specific mailbox. A new mailbox always has a new .ost key value, even if the new mailbox has the same mailbox GUID as the old mailbox.

If a user chooses to work online using a previous version of Outlook, Outlook generates a new .ost file (but the old .ost file is not deleted), and any unsynchronized data in the old .ost file becomes inaccessible. However, if the original database is swapped back in, the previous .ost file becomes readable again, but the current .ost file becomes inaccessible.

This behavior means that, after a disaster occurs in which a dial tone database is created, users must sort and perhaps merge data in multiple .ost files, and then edit their Outlook profiles to redirect those files to their previous .ost file. For more information about this, see "Offline Folders" in Microsoft Knowledge Base article 282496, "XADM: Considerations and Best Practices When Resetting an Exchange Mailbox Database."

The Exchange Recovery Mode in Outlook 2003 was designed to remedy this problem by offering users two options when Outlook 2003 starts after a database reset:

  • Offline mode   If users select Work Offline, they will have access to their current .ost file, but not to their Exchange server. The .ost file will not become permanently inaccessible if they decide to go online.

  • **Online mode   **If users select Connect, they will have access to their new Exchange database, but not to their .ost file. If they want to access items in your offline cache, they can exit Outlook and start again in Offline mode.


    If users needs to transfer items between their .ost file and their Exchange server while in Exchange Recovery Mode, they can do so by adding an Outlook data file (.pst) to their profile. If your users need to do this, instruct them to start Outlook and, on the File menu, point to New, and then click Outlook Data File and follow the prompts to create the file. The new data file will appear in users' folder trees, and the users can then create a folder called \Transfer. Then, the users can drag and drop items from their offline folders to this folder. When the users restart Outlook in Online mode, the Transfer folder and its items will be available.

After the original database has been swapped with the dial tone database, Outlook automatically exits Exchange Recovery Mode the next time the user selects Connect.

If users are not able to preserve their current .ost files with Outlook 2003, perhaps because you cannot restore the original database, they will need to reset their .ost files. For detailed instructions, see How to Reset .ost Files.